Screeder

ABSTRACT

Screeding apparatus for smoothing and finishing the upper surface of freshly poured concrete in the manufacture of precast concrete slabs. The screeder comprises a base frame, including a conveyor for carrying concrete filled forms through the screeder, and a vertically reciprocal screeder carriage upon which are mounted a rotatable drum, pairs of inwardly and outwardly directed scraper blades mounted downstream and upstream of the drum, rollers for engaging the upper flanges of the concrete forms passing through the screeder, wipers curved to the configuration of the drum surface and wiping the edges of the drum, and a final trowel positioned downstream of the drum and extending across the screeder to impart a final finishing and smoothing effect to the concrete as it passes through the screeder. All of the various components mounted on the screeder carriage are adjustable to permit the uncured slabs carried by the forms to be screeded level with the upper edge of the form or at depths below the upper edge of the form if somewhat thinner slabs are being manufactured.

United States Patent 11 1 Shoe et al. 1' July 16, 1974 SCREEDER Primary ExaminerJ. Spencer Overholser [75] Inventors: Theodore W. Shoe, Fletcher; Mark Assistant Examiner-B Tobor [73] Assignee: The Flexicore Co., lnc., Dayton,

01119 57 ABSTRACT [22] Filed: Apr. 19, 1971 Screeding apparatus for smoothing and finishing the upper surface of freshly poured concrete in the manu- [211 Appl l35325 facture of precast concrete slabs. The screeder comprises a base frame, including a conveyor for carrying [52] US. Cl 425/220, 425/218, 425/231 concrete filled forms through the screeder, and a ver- [51] Int. Cl B28b 3/12 tically reciprocal screeder carriage upon which are [58] Field of Search 425/220, 231, 362, 374', mounted a rotatable drum, pairs of inwardly and out- 425/419, 423, 418, 218 wardly directed scraper blades mounted downstream and upstream of the drum, rollers for engaging the [56] References Cited upper flanges of the concrete forms passing through UNITED STATES PATENTS the screeder, wipers curved to the configuration of the 1 drum surface and wiping the edges of the drum, and a gz' z final trowel positioned downstream of the drum and l:578:467 3/1926 mana er 51.: 1:11;... 425/220 extending across the screeder impart a final'finish- 1,977,374 10/1934 Brooke et al. 425/220 x g and Smoothing effect 10 the Concrete as it Passes 2,586,714 2/1952 Richardson et al 425/374 X through the screeder. All of the various components 2,970,361 2/1961 Brown 425/220 X mounted on the screeder carriage are adjustable to 3,122,812 1964 ry 425/220 permit the uncured slabs carried by the forms to be 3 1332 5 1 x32; a 7

screeded levelwith theupper edge ofthe form or at erner 3,523,343 8/1970 Mitchell 425/231 x 333 :9 52: fg zg l sgfi gg tfizg Somewhat R25,7l7 10/1962 Lapidus 425/220X J Wise Bmokvme both of Ohio Attorney, Agent, or Firm-Marechal, Biebel, French &

23 Claims, 14 Drawing Figures PATENTED JUL 1 6 I974 saw u or 5 SCREEDER BACKGROUND THE INVENTION In manufacturing precast concrete structural components it is desirable to provide the components with a smooth exterior finish. This is-particularly true in the manufacture of such things as floor slabs, since the uniformity and smoothness of the slab surfaces will dictate the amount of on site preparation required in order to provide an acceptable subsurface for the application of various flooring materials. Obviously, the less on site operations required the less expensive the construction costs.

In one widely used method of manufacturing precast concrete slabs, prestressing cables and void forming inflatable tubes are first placedin the concrete form and a fairly stiff mix of concrete deposited in the form, encapsulating the inflatable tubes and prestressing cables. The concrete filled form is then vibrated, the upper surface screeded to' remove excess concrete and smooth the upper surface of the concrete, and the concrete filled forms then placed in a kiln for curing at carefully controlled temperatures and humidity. Thereafter, the forms are stripped from the slabs and the slabs cut to customer specifications.

All of these operations are carried out in a carefully planned sequence to provide an efficient manufacturing operation that will produce the maximum number of finished slabs with a givenamount of manufacturing equipment. In the past, one bottle neck in this otherwise highly systematic manufacturing process has been the finishing or screeding operation. Originally, each form was manually screeded by workmen using angle irons or other suitable, flat surfaced members. This operation was then automated to the extent that the angle irons were providedlwith means for mechanically reciprocating them transversely of the forms to smooth and finish the upper surface of the concrete.

Aside from the fact that even this degree of automation did not improve the speed of the screeding operation to the extent desired, it will be apparent that this type of screeder lacks the flexibility necessary to screed different depths of concrete within the form. Therefore, if the manufacturer desired to produce slabs of different thickness it was necessary to have forms of different depths. Since the cost of the forms is a significant factor in the manufacture of precast slabs, it is of course desirable to keep the number of forms necessary to an absolute minimum.

SUMMARY OF THE INVENTION The present invention provides fully automatic screeding apparatus which is capable of screeding concrete slabs of various thickness regardless of the depth of the form being used. The screeding apparatus includes a base frame which supports a series of receiving and collecting troughs, a conveyor for carrying filled concrete forms through the screeding apparatus, and a screed carriage which is vertically reciprocating and carries the concrete finishing and smoothing components.

The carriage rotatably mounts a drum which is slightly shorter in length than the width of the forms being used so that the drum can screed either at a level even with the upper edges of the form or down inside the form if less than full depth slabs are being produced. A pair of wipers are pivotally mounted and engage the drum surface adjacent each of its ends. When the drum is being used to screed full depth slabs, the wipers are positioned in slightly overlappingrelationship to the edges of the drum, thereby preventing the formation of fins of concrete projecting horizontally from the upper edges of the finished slab. When less than full depth slabs are being produced the wipers are positioned inwardly in contact with the ends of the drum surface and the inner surfaces of the concrete forms to prevent theformation of vertically extending fins of concrete on the finished slabs.

The screed carriage is also provided with four wheels, two positioned upstream and two positioned downstream of the drum, which ride the flanges of the forms and prevent the drum from touching the form flanges. This reduces both drum and form wear and prevents the vibration which might otherwise occur as the result of flange-drum contact. Aside from damage to equipment that might result from such vibration, it will be seen that vibration of the concrete carried by the forms may allow the void forming, inflatable tubes to move from their proper positions. The four wheels are, of course, vertically adjustable with respect to the height of the drum to permit the drum to be positioned at various heights with respectto the bottom of the forms passing through the screeding apparatus.

Additionally, the drum is shiftable along its axle so that if some deviation from a perfectly straight side wall on the forms occurs the drum can shift slightly to accommodate this deviation and prevent binding between the ends of the drum and the form inner surfaces. The carriage is raised and lowered bya fluid actuated piston and cylinder mounted at the top of the screed apparatus base frame with the screed carriage pivotally attached to the lower end of the-piston rod.

The screed carriage itself includes an upper platform and downwardly depending side members pivotally attached to the platfonn to provide an articulated assembly. This permits the carriage to shift if, as the rollers ride along-the flanges of the forms passing through the screeding apparatus, one of the flanges is positioned higher than the other. As a result slabs of uniform thickness are produced despite the fact that the flanges of the form do not lie in a common horizontal plane.

The drive motor for the drum is positioned on the upper platform of the screed carriage and since the motor and the lift cylinder are well above the concrete forms there is little danger of their operation being hampered by contamination by the concrete.

The screed carriage also carries a pair of outwardly directed scrapers which engage the flanges of the forms 7 just upstream of the front wheels and a pair of inwardly directed scraper blades which ride the flanges of the forms just upstream of the rear wheels. The scrapers thus clean the flanges of the form to provide a true surface for the wheels of the screed carriage to ride.

Downstream of the rear set of wheels a final trowel is'positioned which extends across the form and is fully adjustable, both vertically and angularly with respect to the surface of the concrete, to impart a final finishing and smoothing to the concrete carried by the forms.

The catch troughs, which aremounted in the base frame beneath the conveyors, include inwardly projecting extensions which shield the bottom flanges of the forms and catch excess concrete removed by the screeding apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the upstream end of the screed apparatus;

FIG. 2 is a vertical elevational view of the drive side of the apparatus;

FIG. 3 is a view taken on line 33 of FIG. 2;

FIG. 4 is an enlarged perspective view showing the downstream end of the screeding apparatus;

FIG. 5 is an endelevational view of the screeding apparatus from the upstream end thereof showing a concrete filled form in cross-section;

FIG. 6 is a plan view of the screeding apparatus of the present invention; 1

FIG. 7 is an enlarged view of a portion of the structure of FIG. 5, partly in section;

FIG. 8 is an enlarged perspective view of a portion of the drum and-wipers;

FIG. 9 is an elevational view of a portion of the screeding apparatus showing one of the rear wheels and the final trowel;

FIG. 10 is a cross sectional view through a concrete filled form having the screeding drum in a lowered position;

FIGS. '11 and 12 show corners of concrete slabs;

FIG. 13 is an end view of one of the form engaging wheels and supporting structure; and

FIG. 14 is a view, partly in section, through the screeder drum.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIGS. 1-6 of the drawings, it will be seen that screeding apparatus 10 in accordance with the present invention includes a base frame having horizontally extending frame members 12 and vertically extending frame members 14. A series of rollers 16 (FIGS. 2,5 and 6) form a conveyor for carrying concrete forms, as at 18, through the screeding apparatus 10 and a pair of collecting and receiving troughs 20 are positioned beneath the conveyor with inwardly directed extensions 22 overhanging and shielding the lower flanges 24 of the forms 18. v

Box beams 26 are fixedto and extend upwardly from the frame members 12 and are suitably interconnected and braced adjacent their upper ends by cross members 28 and 30. Adjacent their lower ends the beams 26- are provided with elongated plates 32 attached thereto by a series of bolts or the like 34 to define four, vertically extending trackways. Cross beams 36 extend between the upper cross members 30 and support a hydraulically or pneumatically operated cylinder 38 having a members 50 are pivotally attached to the platform 42 as at 52and depend downwardly from the platform 42 with their flanges54 received in the vertically extending trackways defined by the box beams 26 and the cover plates 32, as best seen in FIG. 3 of the drawings.

Elongated openings 56 are formed in the webs 58 of the channel members 50 and bearing blocks 60 are mounted on either side of the openings 56 to slidably receive bearings 62. An additional block 68 is affixed by welding or the like to the web 58 of the channel 50 and receives a screw threaded rod 66 adjustable vertically with respectto the block 68 by means of the adjusting nuts 70 (see also FIG. 7). I

The bearings 62 journal a shaft 72 upon which are mounted asprocket 74 adjacent one end thereof and, intermediate the channels 50, a drum 76 which, as seen in FIG. 14,'is slidable along and keyed to theshaft 72, as at 77, and retained in one position along the shaft during certain operations by means of the locking collar 78. A drive motor 80 is mounted on the platform 42 and, through a suitable coupling device 82, drives a drive sprocket 84.

A drive chain 86 is trained about the sprocket 84 and the sprocket 74 to impart driving motions to the shaft 72 and hence, the drum 76. A tensioning device is also mounted on the web 58 of the drive side channel 50 and includes a stub shaft 88 afixed to the web 58 by welding or the like. An arm 90 is attached to the stub shaft 88 by a split ring 92 and the arm 90 carries a short shaft 94 upon which is rotatably mounted the tensioning sprocket 96. g

Channel members 98 are attached to the inner surfaces of the webs of the channels 50 and project, in both upstream and downstream directions, past the vertically extending box beams 26. At their upstream ends the channels 98 carry adjusting mechanism 100, including side plates 102 fixed in spaced apart relationship by spacer blocks 104 and bolts or the like 106. A flat, vertically extending bar 108 is slidably received between the twoplates 102 and carries, adjacent its lower end, a shaft 1 10 rotatably mounting a front wheel 112.

Also attached to the bars 108 arehorizontally extending bars 114 which carry angle members 116 at their forward ends to which, in turn, are attached plate members 118. The plate members 118 serve as backing plates and cooperate with additional plates 120 (see also FIGS. 1 and 6) to sandwich a resilient strip 122 therebetween. Each of the bars 108, as seen in FIG. 13, are provided with a series of openings 123 therethrough spaced apart vertically certain predetermined distances and a connecting pin 124 extends through the plates 102 and an opening 123 to vertically position the wheel 112 at the desired height with respect to the rest of the screed carriage.

As noted above, the channels 98 extend past the beams 26 inboth upstream and downstream directions. At their downstream'ends the channels 98 carry adjust-t ing and support mechanism 126 substantially identical to the supporting and adjusting mechanism 100, with the exception that the side plates'1-02 are replaced with larger side plates 128, and the downstream spacer bars are somewhat wider than its counterparts in the upstream mechanisms 100. I

Additionally, it will be noted that the plates 118 at the downstream end of the channels are inwardly rather than outwardly directed. Aside from these differences the structure 126 is identical to the structure 100 and like parts are identified by like reference numberals. As best seen in FIGS. 1 and 9, the extra width of the plates 128 is required to provide support for a pair of depending bars 132, across the lower ends of which are attached a flat plate 134.

A shaft 136 is also received in the lower ends of the members 132 and a pair of arms 138 are loosely mounted on the shaft 136 and extend downstream therefrom. An angle number 140 also extends between the arms 138 and is affixed thereto by welding or the like. A bolt 142 is threadably received through one web of the angle member 140 and bears against the upper surface of the plate 134. A second pair of arms144 are pivotally attached to and depend downwardly from the arms 138 and carry a trowel 146 adjacent their lower end.

Each of the arms 138 also carry downwardly depending blocks 148 through which are threadably received bolts 150. Angle iron'140 also threadably receives a Each of the support structures 154 include vertically extending angle members 156 to which are affixed inner and outer cross members 158. The angle members-156 also carry short shafts 162 which pivotally mount vertically depending wiper arms 164 on the support structure 154. Bolts 166 are threadably received through the cross members 158 and bear on opposite sides of the depending arms 164. It will also be noted from FIG. 8 that a'wiper or doctor blade 167 bears against the surface of the drum 76 upstream of the axis thereof. Blade 167 prevents concrete from being car ried back around the drum and into the concrete form.

At their lower ends members 164 carry strips of resil-.

ient material 168 which are curved on their downstream faces to conform with that portion of the surface of the drum 76 which they engage. A hydraulic or pneumatic piston and cylinder 170, which is omitted from FIG. 8 for purposes of clarity but which is shown in FIG. 7 of the drawings, extends between the arms 164 and is pivotally attached thereto as at 172 and 174. Thus,movement of the piston rod 176 into and out of the cylinder 178 will permit the arms 164 to pivot between the limits set by the threaded stop members 166.

With the above construction it will be seen that a form 18 filled with concrete is conveyed through the screeding apparatus 10 by means of the rollers 16 in the direction indicated by the arrow in FIG. 4 of the drawings. As the form moves through the screeding apparatus the upper flanges 180 of the form are cleaned by the upstream scraper blades 122 to provide a smooth clear surface for the upstream rollers 112 to ride on.

The relative vertical positions of the rollers, scrapers and trowel with respect to the lower surface of the drum 76 are adjusted by means of the pins 124 and the various openings 123 in which the pins are received. Thus, with the pins 124 received within the upper most ones of the vertically spaced openings 123, the lower surfaces of the rollers 112, scrapers 122, trowel 146 and drum 76 will be substantially co-planar.

Thus, with the four rollers 112 riding on the upper flanges 180 of the forms 18 the drum 76 will be positioned substantially as shown in FIGS. 5, 7 and 14 of the drawings. As the concrete filled forms 18 move past 6 the upstream wheels 112 any concrete lying on the upper flanges 180 is scraped therefrom by the scraper blades 122 back into the forms 18.

Continued movement of the form carries it beneath the rotating drum 76, which smooths the surface of the concrete and removes any excess therefrom. The wipers 68 are positioned in slightly overlaping relationship to the ends of the drum 76 to wipe a portion of the flanges 180 and a portion of the drum 76 and thereby prevent the formation of horizontally extending fins 182 shown in FIG. 11 of the drawings. The wipers, in conjunction with the upstream scrapers,,also provide another important function. Thus, concrete directed inwardly by the upstream scrapers is retained between the wipers against the upstream surface of the drum. The wipers, therefore serve as end dams to hold a supply of concrete which will compensate for low spots. This of course renders less critical the placement of the right amount of concrete in the forms.

As the form continues through the screedingapparatus the downstream scrapers 122 clean the flanges 180 and direct any excess concrete lying thereon onto the ceiving trough 20, as indicated by the arrow in FIG. 4

of the drawings. The downstream wheels 112, there fore, are also provided with a clean surface to ride on as the form passes through the screeding apparatus.

Lastly, theform 18 encounters the trowel 146, which imparts a final smoothing and finishing to the concrete carried by the form. The vertical position of trowel 1-46 with respect to the upper edge of the form is controlled by threading the bolt 142 through the horizontal-leg of the angle with the lower end of the bolt 142 bearing on the plate 134. The angular position of the trowel 146 with respectto the surface of the concrete may also be varied by threading the bolts 150 and 152 through the depending plates 148 and the vertically extending leg of the angle 140, respectively.

As noted above, the entire screed carriage is movable along the trackways defined by the surfaces of the box beams 26 and the plates 32 attached thereto and the pressure with which the drum 76 bears against the concrete carried by, the form 18 is controlled by the cylinder 38, which in turn is controlled by suitable circuitry, not shown. Additionally, it will be seen that the bearings 63 for the drum shaft 72 are vertically adjustable in the channels 50 by means of the threaded member 66 as will be apparent from inspection of FIGS. 4 and 7 of the drawings.

It will further be noted that the channels 50 are pivotally attached to the upper platform 42 of the screed carriage and that the upper platform 42 is pivotally attached to the lower end of the piston rod 40. This provides an articulated structure which permits the opposite sides of the screed carriage to shift if the form passing through the screeding apparatus is tilted so that one flange is higher than the other. Thus, upon an occurence of this sort, the screeding apparatus will still provide a finished slab of uniform depth transversely thereof.

As noted previously, it will often be desirable to produce slabs of thicknesses less than that of the full depth of forms 18. If this is thecase, it is merely necessary to reposition the pins 124 in'the appropriate openings in the bars 108. This will have the effect of lowering the lower surface of the drum 76 below the lower surfaces of the rollers l12'and the scrapers 122. The wipers 168,

also be lowered with the drum 76.

With this configuration, the drum 76, being less in axial length than the width of the forms passing through the screeding apparatus, will be positioned down in the form as shown somewhat schematically in FIG. of the drawings. Before positioning the drum 76 in this manner the wiper arms 164 are pivoted inwardly by means of the piston and cylinder 170 so that the outer surfaces of the wipers 168 clear the inner faces of the forms. The cylinder 70 is then pressurized, forcing the wipers outwardly to bear against inner surfaces of the form while still contacting a portion of the surface of the roller 76 adjacent each end thereof. This prevents the formation of a fin, as shown in FIG. .12 at 184, from forming along each of the upper edges of the finished slab.

The trowel 146, is of course, pivoted around the shaft 136, clockwise as seen in FIG. 9 of the drawings, to an inoperative position. Additionally, when screeding flow or with the drum 76 within the, form as shown in FIG. 10 of the drawings, it will usually be desired to loosen the locking collars 78 to permit the drum 76 to slide axially along the shaft 72. Thus, if the side walls of the form 18 are not perfectly straight the drum 76 can accommodate this deviation by shifting along its axle 72.

The maximum speed of rotation of the drum 76 will be determined by a variety of factors such as the stiffness of the concrete mix, the rate of speed of the form passing through the screeding apparatus, etc. To accommodate variations in these factors the speed of the drum 76 can be readily varied by changing the diameter of the sprockets utilized, with the tensioning sprocket 96 maintaining the chain 86 taut despite changes in sprocket size.

From the above it will be apparent that the present invention provides screeding apparatus which automatically provides a smooth, true, uniform surface to concrete slabs and is extremely flexible and adapted to operate under a variety of manufacturing conditions.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention.

What is claimed is:

1. Apparatus of the type described comprising:

a. abase frame,

b. means-for conveying a concrete form through said base frame,

c. a vertically reciprocal screed carriage,

(1. means mounting said screed carriage for reciprocal movement on said base frame toward and away from said conveying means,

e. a rotatable cylindrical drum having an axial length 7 less than, but substantially equal to,'the internal width of concrete forms conveyed through said base frame by said conveying means, and

f. means rotatably mounting said drum on said screed carriage with the axis of rotation of said drum extending normal to the directionof travel of concrete forms conveyed through said base frame by said conveying means.

2. The apparatus of claim 1 further comprising:

a. means for varying the pressure with which said drum engages concrete in forms carried therebeneath by said conveying means.

3. The apparatus of claim 1 further comprising:

. a. a fluid actuated piston and cylinder, and

b. means attaching said piston and cylinder to said base frame and carriage to cause relative movement therebetween in response to relative movement between said piston and cylinder.

4. The apparatus of claim 1 further comprising:

a. form engaging means mounted on said carriage and engageable with concrete forms conveyed through said base frame to position the surface of said drum'with respect to concrete carried by said form.

S. The apparatus of claim 4 wherein:

a. said form engaging means comprises rollers rotatably mounted onsaid carriage.

6. The apparatus of claim 4 wherein:

a. said form engaging means comprises spaced pairs of rollers, and

b. means rotatably mounting said pairsof rollers on opposite sides of said drum.

7. The apparatus of claim 4 further comprising:

a. means for adjusting with respect to each other the height of said drum and said'form engaging means above said conveying means.

8. The apparatus of claim 1 further comprising:

a. means for scraping portions of concrete forms being conveyed, through said base frame, and

b. means mountingsaid scraping means on said carr age.

9. The apparatus of claim 8 wherein said scraping.

means includes:

a. a first set of opposed scraper blades mounted on one side of said drum.

10. The apparatus of claim 9 wherein said scraping means includes:

a. a second set of opposed scraper blades mounted on a side of said drum opposite said one side.

11. The apparatus of claim 1 further comprising:

a. wiper means engaging the surface of said drum adjacent each end thereof.

12. The apparatus of claim 11 further comprising:

a. wiper arms each pivotally mounted adjacent one end thereof on said carriage,

b. means mounting said wiper means on opposite ends of said wiper arms, and

c. means for pivoting said wiper arms.

13. The apparatus of claim 1 further comprising:

.a. trowel means extending transversely of said base frame downstream of said drum.

14. The apparatus of claim 13 further comprising:

a. means for varying the angular disposition of said trowel means with respect to the upper surface of concrete contained in a form conveyed through said base frame by said conveying means.

15. The apparatus of claim 1 further comprising:

a. receiving troughs mounted on said base frame for receiving excess concrete screeded from concrete filled forms conveyed through said base frame.

16. The apparatus of claim 1 wherein said screed carriage mounting means comprises:

a. substantially vertically extending trackways on said base frame, and I b. portions of said screed carriage engaged with and movable along said trackways.

17. The apparatus of claim 1 further comprising; a. means pivotally attaching said screed carriage to said mounting means. 18. The apparatus of claim 17 wherein said screed carriage comprises:

a. an upper platform pivotally attached to said mounting means by said pivotally attaching means,

b. downwardly depending side members, and

0. means pivotally attaching said side members to opposite sides of said upper platform.

19. The apparatus of claim 18 further comprising:

a. substantially vertically extending trackways on said base frame, and

b. portions of said side members engaged with and movable along said trackways.

20. Apparatus of the type described comprising:

a. a base frame having an upstream end and a downstream end,

b. conveyor means mounted in said base frame for conveying concrete filled forms therethrough in a downstream direction,

c. a screed carriage mounted on said base frame for movement toward and away from said conveyor means,

d. a drum rotatably mounted on said carriage,

e. a first pair of scrapers mounted on said carriage upstream of said drum and angularly disposed outwardly in an upstream direction,

f. a second pair of scrapers mounted on said carriage downstream of said drum and angularly disposed inwardly in said upstream direction,

g. a pair of drum wipers engaging the surface of said drum adjacent each end thereof, and

h. a trowel extending across said conveyor means downstream of said second pair of scrapers.

21. The apparatus of claim 20 further comprising:

a. means for moving said drum wipers axially of said drum.

22. The apparatus of claim 20 further comprising:

a. means for varying the relative vertical positions of said scrapers and said drum with respect to each other.

23. The apparatus of claim 20 wherein:

a. said base frame includes vertical trackways engaged by portions of said screed carriage accommodating said movement toward and away from said conveyor means, and

b. piston and cylinder means attached to said base along said trackways. 

1. Apparatus of the type described comprising: a. a base frame, b. means for conveying a concrete form through said base frame, c. a vertically reciprocal screed carriage, d. means mounting said screed carriage for reciprocal movement on said base frame toward and away from said conveying means, e. a rotatable cylindrical drum having an axial length less than, but substantially equal to, the internal width of concrete forms conveyed through said base frame by said conveying means, and f. means rotatably mounting said drum on said screed carriage with the axis of rotation of said drum extending normal to the direction of travel of concrete forms conveyed through said base frame by said conveying means.
 2. The apparatus of claim 1 further comprising: a. means for varying the pressure with which said drum engages concrete in forms carried therebeneath by said conveying means.
 3. The apparatus of claim 1 further comprising: a. a fluid actuated piston and cylinder, and b. means attaching said piston and cylinder to said base frame and carriage to cause relative movement therebetween in response to relative movement between said piston and cylinder.
 4. The apparatus of claim 1 further comprising: a. form engaging means mounted on said carriage and engageable with concrete forms conveyed through said base frame to position the surface of said drum with respect to concrete carried by said form.
 5. The apparatus of claim 4 wherein: a. said form engaging means comprises rollers rotatably mounted on said carriage.
 6. The apparatus of claim 4 wherein: a. said form engaging means comprises spaced pairs of rollers, and b. means rotatably mounting said pairs of rollers on opposite sides of said drum.
 7. The apparatus of claim 4 further comprising: a. means for adjusting with respect to each other the height of said drum and said form engaging means above said conveying means.
 8. The apparatus of claim 1 further comprising: a. means for scraping portions of concrete forms being conveyed through said base frame, and b. means mounting said scraping means on said carriage.
 9. The apparatus of claim 8 wherein said scraping means includes: a. a first set of opposed scraper blades mounted on one side of said drum.
 10. The apparatus of claim 9 wherein said scraping means includes: a. a second set of opposed scraper blades mounted on a side of said drum opposite said one side.
 11. The apparatus of claim 1 further comprising: a. wiper means engaging the surface of said drum adjacent each end thereof.
 12. The apparatus of claim 11 further comprising: a. wiper arms each pivotally mounted adjacent one end thereof on said carriage, b. means mounting said wiper means on opposite ends of said wiper arms, and c. means for pivoting said wiper arms.
 13. The apparatus of claim 1 further comprising: a. trowel means extending transversely of said base frame downstream of said drum.
 14. The apparatus of claim 13 further comprising: a. means for varying the angular disposition of said trowel means with respect to the upper surface of concrete contained in a form conveyed through said base frame by said conveying means.
 15. The apparatus of claim 1 further comprising: a. receiving troughs mounted on said base frame for receiving excess concrete screeded from concrete filled forms conveyed through said base frame.
 16. The apparatus of claim 1 wherein said screed carriage mounting means comprises: a. substantially vertically extending trackways on said base frame, and b. portions of said screed carriage engaged with aNd movable along said trackways.
 17. The apparatus of claim 1 further comprising: a. means pivotally attaching said screed carriage to said mounting means.
 18. The apparatus of claim 17 wherein said screed carriage comprises: a. an upper platform pivotally attached to said mounting means by said pivotally attaching means, b. downwardly depending side members, and c. means pivotally attaching said side members to opposite sides of said upper platform.
 19. The apparatus of claim 18 further comprising: a. substantially vertically extending trackways on said base frame, and b. portions of said side members engaged with and movable along said trackways.
 20. Apparatus of the type described comprising: a. a base frame having an upstream end and a downstream end, b. conveyor means mounted in said base frame for conveying concrete filled forms therethrough in a downstream direction, c. a screed carriage mounted on said base frame for movement toward and away from said conveyor means, d. a drum rotatably mounted on said carriage, e. a first pair of scrapers mounted on said carriage upstream of said drum and angularly disposed outwardly in an upstream direction, f. a second pair of scrapers mounted on said carriage downstream of said drum and angularly disposed inwardly in said upstream direction, g. a pair of drum wipers engaging the surface of said drum adjacent each end thereof, and h. a trowel extending across said conveyor means downstream of said second pair of scrapers.
 21. The apparatus of claim 20 further comprising: a. means for moving said drum wipers axially of said drum.
 22. The apparatus of claim 20 further comprising: a. means for varying the relative vertical positions of said scrapers and said drum with respect to each other.
 23. The apparatus of claim 20 wherein: a. said base frame includes vertical trackways engaged by portions of said screed carriage accommodating said movement toward and away from said conveyor means, and b. piston and cylinder means attached to said base frame and said carriage for moving said carriage along said trackways. 